Testing

This guide covers testing strategies for EventFlux applications, from unit tests to integration tests.

AppRunner Test Helper

The AppRunner is the primary testing utility for EventFlux applications:

use eventflux::testing::AppRunner;

#[test]
fn test_basic_filter() {
    let app = r#"
        DEFINE STREAM Input (value INT);

        SELECT value
        FROM Input
        WHERE value > 10
        INSERT INTO Output;
    "#;

    let runner = AppRunner::new(app, "Output");

    // Send test events
    runner.send("Input", vec![
        event![5],   // Should be filtered
        event![15],  // Should pass
        event![8],   // Should be filtered
        event![20],  // Should pass
    ]);

    // Get results and verify
    let results = runner.shutdown();
    assert_eq!(results.len(), 2);
    assert_eq!(results[0].get::<i32>(0), Some(15));
    assert_eq!(results[1].get::<i32>(0), Some(20));
}

Testing Patterns

Testing Filters

#[test]
fn test_temperature_filter() {
    let app = r#"
        DEFINE STREAM Sensors (sensor_id STRING, temp DOUBLE);

        SELECT sensor_id, temp
        FROM Sensors
        WHERE temp > 100.0
        INSERT INTO Alerts;
    "#;

    let runner = AppRunner::new(app, "Alerts");

    runner.send("Sensors", vec![
        event!["s1", 95.0],
        event!["s2", 105.0],
        event!["s3", 98.0],
        event!["s4", 110.0],
    ]);

    let results = runner.shutdown();
    assert_eq!(results.len(), 2);

    // Verify specific values
    assert_eq!(results[0].get::<String>(0), Some("s2".to_string()));
    assert_eq!(results[1].get::<String>(0), Some("s4".to_string()));
}

Testing Aggregations

#[test]
fn test_sum_aggregation() {
    let app = r#"
        DEFINE STREAM Sales (product STRING, amount DOUBLE);

        SELECT product, SUM(amount) AS total
        FROM Sales
        WINDOW LENGTHBATCH(3)
        GROUP BY product
        INSERT INTO Totals;
    "#;

    let runner = AppRunner::new(app, "Totals");

    runner.send("Sales", vec![
        event!["A", 10.0],
        event!["A", 20.0],
        event!["A", 30.0],  // Batch completes here
    ]);

    let results = runner.shutdown();
    assert_eq!(results.len(), 1);
    assert_eq!(results[0].get::<f64>(1), Some(60.0));
}

Testing Windows

#[test]
fn test_length_window() {
    let app = r#"
        DEFINE STREAM Numbers (value INT);

        SELECT AVG(value) AS avg_value
        FROM Numbers
        WINDOW LENGTH(3)
        INSERT INTO Averages;
    "#;

    let runner = AppRunner::new(app, "Averages");

    // Window fills up
    runner.send("Numbers", vec![event![10]]);  // avg = 10
    runner.send("Numbers", vec![event![20]]);  // avg = 15
    runner.send("Numbers", vec![event![30]]);  // avg = 20

    // Window slides
    runner.send("Numbers", vec![event![40]]);  // [20, 30, 40] avg = 30

    let results = runner.shutdown();

    // Verify sliding window behavior
    assert!(results.len() >= 4);
}

Testing Joins

#[test]
fn test_stream_join() {
    let app = r#"
        DEFINE STREAM Orders (order_id STRING, customer_id STRING);
        DEFINE STREAM Payments (order_id STRING, amount DOUBLE);

        SELECT o.order_id, o.customer_id, p.amount
        FROM Orders AS o
        WINDOW LENGTHBATCH(2)
        JOIN Payments AS p
          ON o.order_id = p.order_id
        INSERT INTO Matched;
    "#;

    let runner = AppRunner::new(app, "Matched");

    runner.send("Orders", vec![event!["O1", "C1"]]);
    runner.send("Payments", vec![event!["O1", 100.0]]);
    runner.send("Orders", vec![event!["O2", "C2"]]);
    runner.send("Payments", vec![event!["O2", 200.0]]);

    let results = runner.shutdown();
    // Verify join results
    assert!(!results.is_empty());
}

Testing Patterns

#[test]
fn test_sequence_pattern() {
    let app = r#"
        DEFINE STREAM Events (event_type STRING, value INT);

        FROM Events
        MATCH (e1=Event -> e2=Event)
        WITHIN 1 MINUTE
        FILTER e1.event_type = 'START' AND e2.event_type = 'END'
        SELECT e1.value AS start_value, e2.value AS end_value
        INSERT INTO Sequences;
    "#;

    let runner = AppRunner::new(app, "Sequences");

    runner.send("Events", vec![
        event!["START", 1],
        event!["END", 2],
    ]);

    let results = runner.shutdown();
    assert_eq!(results.len(), 1);
    assert_eq!(results[0].get::<i32>(0), Some(1));
    assert_eq!(results[0].get::<i32>(1), Some(2));
}

Advanced Testing

Testing Multiple Outputs

#[test]
fn test_multiple_outputs() {
    let app = r#"
        DEFINE STREAM Input (value INT);

        SELECT value FROM Input WHERE value > 50 INSERT INTO High;
        SELECT value FROM Input WHERE value <= 50 INSERT INTO Low;
    "#;

    // Test high output
    let high_runner = AppRunner::new(app, "High");
    high_runner.send("Input", vec![event![30], event![70], event![40], event![80]]);
    let high_results = high_runner.shutdown();
    assert_eq!(high_results.len(), 2);

    // Test low output
    let low_runner = AppRunner::new(app, "Low");
    low_runner.send("Input", vec![event![30], event![70], event![40], event![80]]);
    let low_results = low_runner.shutdown();
    assert_eq!(low_results.len(), 2);
}

Testing with Time Advancement

#[test]
fn test_time_window() {
    let app = r#"
        DEFINE STREAM Events (ts LONG, value INT);

        SELECT COUNT(*) AS count
        FROM Events
        WINDOW TUMBLING(5 sec)
        INSERT INTO Counts;
    "#;

    let runner = AppRunner::new(app, "Counts");

    // Events in first window
    runner.send_with_time("Events", vec![
        event![1000i64, 1],
        event![2000i64, 2],
        event![3000i64, 3],
    ], 1000);

    // Advance time to trigger window
    runner.advance_time(6000);

    // Events in second window
    runner.send_with_time("Events", vec![
        event![6000i64, 4],
        event![7000i64, 5],
    ], 6000);

    runner.advance_time(11000);

    let results = runner.shutdown();
    assert_eq!(results[0].get::<i64>(0), Some(3)); // First window
    assert_eq!(results[1].get::<i64>(0), Some(2)); // Second window
}

Testing Error Conditions

#[test]
fn test_invalid_query() {
    let manager = EventFluxManager::new();

    let result = manager.create_runtime("INVALID SQL QUERY");
    assert!(result.is_err());

    if let Err(EventFluxError::ParseError(msg)) = result {
        assert!(msg.contains("syntax"));
    }
}

#[test]
fn test_stream_not_found() {
    let app = r#"
        DEFINE STREAM Input (value INT);
        SELECT value FROM Input INSERT INTO Output;
    "#;

    let manager = EventFluxManager::new();
    let runtime = manager.create_runtime(app).unwrap();

    let result = runtime.send("NonExistent", event![42]);
    assert!(matches!(result, Err(EventFluxError::StreamNotFound(_))));
}

Test Organization

Recommended Structure

tests/
├── unit/
│   ├── filter_tests.rs
│   ├── window_tests.rs
│   ├── join_tests.rs
│   └── pattern_tests.rs
├── integration/
│   ├── end_to_end_tests.rs
│   └── performance_tests.rs
└── common/
    └── mod.rs  # Shared test utilities

Shared Test Utilities

// tests/common/mod.rs
use eventflux::testing::AppRunner;

pub fn create_sensor_app() -> &'static str {
    r#"
        DEFINE STREAM Sensors (sensor_id STRING, value DOUBLE);

        SELECT sensor_id, value
        FROM Sensors
        WHERE value > 100.0
        INSERT INTO Alerts;
    "#
}

pub fn send_sensor_events(runner: &AppRunner, count: usize) {
    for i in 0..count {
        runner.send("Sensors", vec![
            event![format!("s{}", i), (i as f64) * 10.0],
        ]);
    }
}

Property-Based Testing

Using proptest for property-based testing:

use proptest::prelude::*;
use eventflux::testing::AppRunner;

proptest! {
    #[test]
    fn filter_preserves_order(values in prop::collection::vec(any::<i32>(), 0..100)) {
        let app = r#"
            DEFINE STREAM Input (value INT);
            SELECT value FROM Input WHERE value > 0 INSERT INTO Output;
        "#;

        let runner = AppRunner::new(app, "Output");

        for v in &values {
            runner.send("Input", vec![event![*v]]);
        }

        let results = runner.shutdown();
        let result_values: Vec<i32> = results
            .iter()
            .filter_map(|e| e.get::<i32>(0))
            .collect();

        // Verify order is preserved
        let expected: Vec<i32> = values.into_iter().filter(|&v| v > 0).collect();
        prop_assert_eq!(result_values, expected);
    }
}

Best Practices

Testing Guidelines

Test one thing at a time - Each test should verify a single behavior
Use descriptive names - Test names should describe the scenario
Test edge cases - Empty inputs, boundary values, etc.
Keep tests fast - Use small data sets
Make tests deterministic - Avoid time-dependent tests when possible

Common Pitfalls

Race conditions - Use single-threaded config for determinism
Timing issues - Use explicit time advancement
Flaky tests - Ensure proper synchronization
Over-mocking - Test real behavior when practical

Next Steps

Configuration - Configure test environments
SQL Reference - Query syntax for tests
Architecture - Understand internals for debugging

AppRunner Test Helper​

Testing Patterns​

Testing Filters​

Testing Aggregations​

Testing Windows​

Testing Joins​

Testing Patterns​

Advanced Testing​

Testing Multiple Outputs​

Testing with Time Advancement​

Testing Error Conditions​

Test Organization​

Recommended Structure​

Shared Test Utilities​

Property-Based Testing​

Best Practices​

Next Steps​

AppRunner Test Helper

Testing Patterns

Testing Filters

Testing Aggregations

Testing Windows

Testing Joins

Testing Patterns

Advanced Testing

Testing Multiple Outputs

Testing with Time Advancement

Testing Error Conditions

Test Organization

Recommended Structure

Shared Test Utilities

Property-Based Testing

Best Practices

Next Steps